Three tiers of an exposure assessment are being implemented. Tier 1 enrolls and interviews cases and controls seeking to identify risk factors, including residential and occupational chemical exposures. In Tier 2, cases and birth certificate controls that have not changed residence based on specific criteria are part of a reliability study, which seeks to determine if self-reported chemicals used at the time of interview are found in the home during a visual survey several months after interview. Tier 3 aims to document the potential for household exposures by sampling dust on the floor surfaces. The objective is to identify if there are differences in concentrations of pesticides, metals, polyaromatic hydrocarbons, cotinine, polychorinated biphenyls, and ethylenethiourea in the homes of cases and controls. Further, a case-case analysis will identify if cases with chromosomal translocations of interest live in homes with higher concentrations of target compounds than cases that do not have such translocations. These analyses will determine whether leukemic children with common genetic changes experience common exposures and whether these genetic changes have approximately the same temporal occurrence. Finally, we will evaluate whether children with and without leukemia differ with respect to susceptibility.